jenkins: add script for clang

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
testing: don't run all examples in jenkins

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
tests: Jenkins does not clean the workspace

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>